Re: [HACKERS] CLUSTER command progress monitor

On Fri, Sep 6, 2019 at 5:11 AM Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> On Fri, Sep 6, 2019 at 1:44 AM Michael Paquier <michael(at)paquier(dot)xyz> wrote:
> > I don't see exactly why we could not switch to a fixed number of
> > slots, say 8, with one code path to start a progress which adds an
> > extra report on the stack, one to remove one entry from the stack, and
> > a new one to reset the whole thing for a backend. This would not need
> > much restructuration of course.
>
> You could do that, but I don't think it's probably that great of an
> idea. Now you've built something which is significantly more complex
> than the original design of this feature, but still not good enough to
> report on the progress of a query tree. I tend to think we should
> confine ourselves to the progress reporting that can reasonably be
> done within the current infrastructure until somebody invents a really
> general mechanism that can handle, essentially, an EXPLAIN-on-the-fly
> of a current query tree.

+1. Let's not complicate the progress reporting infrastructure for an
uncertain benefit.

CLUSTER/VACUUM FULL is fundamentally an awkward utility command to
target with progress reporting infrastructure. I think that it's okay
to redefine how progress reporting works with CLUSTER now, in order to
fix the REINDEX/CLUSTER state clobbering bug.

--
Peter Geoghegan